Microelectromechanical System (MEMS) microphones have been used throughout the years. These devices include a back plate (or charge plate), a diaphragm, and other components. In operation, sound energy moves the diaphragm, which causes an electrical signal to be created at the output of the device and this signal represents the sound energy that has been received.
These microphones typically use amplifiers or other circuitry that further processes the signal obtained from the MEMS component. In some examples, a differential amplifier is used that obtains a difference signal from the MEMS device.
In these applications, the Signal-To-Noise ratio (SNR) is desired to be high since a high SNR signifies that less noise is present in the system. However, achieving a high SNR ratio is difficult to achieve. For example, different sources of noise are often present (e.g., power supply noise, RF noise, to mention two examples). In systems that use differential amplifiers, it is possible to reduce correlated (common mode) noise as well as increasing signal to noise ratio via the subtraction of the signals from the differential pair.
In previous systems, various attempts to negate noise in have generally been unsuccessful. As a result, user dissatisfaction with these previous systems has resulted.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding respective areas of inquiry and study except where specific meanings have otherwise been set forth herein.